The Borodin by Borodin are indeed spectacular. For "Death and the Maiden" there are excellent recordings by the Emerson and Tokyo, and the best of all is the Busch Quartet from the 1930s (which can be found, or could once, on EMI/Angel CD: don't sweat the dated sound, it's surprisingly vivid). You might want to try the Brahms quartets (Alban Berg, Takacs are good), the Bartok (Tokyo, Emerson, best of all Vegh), the Janacek (Tokyo, Smetana). These are some of m favorites!